CVE-2025-6069
HTMLParser quadratic complexity when processing malformed inputs
- State
- Published
- Severity
- 4.3 Medium
- Published
- Jun 17, 2025
- Updated
- Jul 31, 2026
- Reserved
- Jun 13, 2025
Description
The html.parser.HTMLParser class had worse-case quadratic complexity when processing certain crafted malformed inputs potentially leading to amplified denial-of-service.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 4.3 Medium | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | PSF |
Weaknesses
- CWE-1333 Inefficient Regular Expression Complexity
Affected Products
| Product | Versions |
|---|---|
CPythonPython Software Foundation |
|
References
- https://github.com/python/cpython/issues/135462issue-tracking
- https://github.com/python/cpython/pull/135464patch
- https://github.com/python/cpython/commit/4455cbabf991e202185a25a631af206f60bbc949patch
- https://github.com/python/cpython/commit/6eb6c5dbfb528bd07d77b60fd71fd05d81d45c41patch
- https://github.com/python/cpython/commit/d851f8e258c7328814943e923a7df81bca15df4bpatch
- https://mail.python.org/archives/list/security-announce@python.org/thread/K5PIYLR6EP3WR7ZOKKYQUWEDNQVUXOYM/vendor-advisory
- https://github.com/python/cpython/commit/8d1b3dfa09135affbbf27fb8babcf3c11415df49patch
- https://github.com/python/cpython/commit/ab0893fd5c579d9cea30841680e6d35fc478afb5patch
- https://github.com/python/cpython/commit/f3c6f882cddc8dc30320d2e73edf019e201394fcpatch
- https://github.com/python/cpython/commit/fdc9d214c01cb4588f540cfa03726bbf2a33fc15patch
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